A composite video signal comprises a luminance signal (Y) and a chrominance signal (C). A comb filter is commonly used to separate the luminance signal and the chrominance signal from the composite video signal. The process of separating the luminance signal and the chrominance signal is referred to as a Y/C separation.
There are three types of comb filters used to separate the luminance signal and the chrominance signal of the composite video signal. The three types of comb filters include a one-dimensional (1D) comb filter, a two-dimensional (2D) comb filter and a three-dimensional (3D) comb filter. The 1D comb filter and the 2D comb filter are referred to as non-3D comb filters. In general, the non-3D comb filter is used to separate the luminance signal and the chrominance signal when a frame is under a motion condition, and the 3D comb filter is used to separate the luminance signal and the chrominance signal when the frame is under a static condition.
Particularly, the 1D comb filter or the 2D comb filter is selected to provide an output thereof according to points of the frame. When a luminance signal of one point is determined to be more similar to luminance signals of neighboring points adjacent to the one point in a horizontal direction, the 1D comb filter is selected. When the luminance signal of the one point is determined to be more similar to luminance signals of neighboring points adjacent to the one point in a vertical direction, the 2D comb filter is selected. However, a saw-tooth or sparkling situation occurs because of inharmonious switching between the 1D comb filter and the 2D comb filter.
Therefore, there is a need for a solution to avoid the occurrence of the saw-tooth or sparkling situation because of the inharmonious switching between the 1D comb filter and the 2D comb filter.